The invention presented concerns the filtration of liquids. In particular machines for grinding, electric arc erosion and other metal machining methods, in which the metal removal process must be cooled with oil or emulsion, are equipped with a coolant conditioning unit, the purpose of which is to clean the coolant leaving the working area of solid particles, e.g. metal and grinding wheel particles, in the following called deposit, and to subsequently re-channel it into the process. In processes involving high metal removal rates, up to 200 liters/min. are fed into the machine under high pressure. But also in other processes the task of separating solid particles from liquids with high efficiency, quality and availability is frequently encountered, which strives after a deposit as dry as possible and a long filter life.
In the field principally considered here, i.e. the filtering of coolants for chip-removing machine tools, the cleaning of the coolant from metal chips and other solid particles involved in the process is mostly effected with centrifuges or filtering plants using band or gap filters, or other types of filter element.
The known centrifuges have the advantage of requiring no actual filter, andxe2x80x94thanks to the centrifugal actionxe2x80x94permit a lower residual liquid content in the deposit than with the known true filter units. Due to the limitations on the control of the centrifuge size and speed under high purity requirements, however, their filtration rate is restricted to outputs which are inadequate for processes involving high liter flowrate.
The limitations of the known band filter units for high liter flowrate and filtering quality lie in their high space requirements, the controllability of liquids carrying solid particles of varying consistency and size with respect to filter clogging, and in the high residual liquid content, whichxe2x80x94where the relevant demands are highxe2x80x94make a subsequent separate drying of the deposit necessary.
In the case of known filtering units with tube-shaped filter elements, a high liter flowrate can even be achieved in modest space conditions and under high purity demands, and the filter tubes have a long life duration. However, depending on the nature and consistency of the deposit, problems arise in the filter re-generation phase with respect to detachment of the deposit from the filter surface, and the discharge of the deposit from the pressure vessel. Moreover here too the deposit is too laden with residual liquid, and must be dried in an additional operation before being discarded.
The objective of the present invention therefore consists in introducing a process and an apparatus by which, under modest space requirements and at high liter flowrates, the liquid can be efficiently cleansed and the deposit dried. In accordance with the invention, the functions
Filtration
Regeneration of the filter and
Drying of the deposit are fulfilled in a single apparatus, where the filtered liquid, the polluted residual liquid from the deposit, and the dried deposit leave the apparatus independent of each other by different discharge openings.